More than 15 kilometres through underground gas pipelines, beneath the battlefield in northeastern Ukraine.
That was the extraordinary route taken by Ukrainian troops in a daring operation near Kupiansk in the Kharkiv region, turning a tactic once used by Moscow's forces against them.
Codenamed Operation Veles, the mission saw Ukrainian soldiers infiltrate Russian positions through underground pipelines infrastructure, with Volodymyr Zelenskyy revealing on Tuesday that more than 100 Russian troops had been eliminated and over 30 captured.
